The piece of paper that fooled Hitler

It was an audacious double-cross that fooled the Nazis and shortened World War II. Now a document, here published for the first time, reveals the crucial role played by Britain's code-breaking experts in the 1944 invasion of France.

All the ingredients of a gripping spy thriller are there - intrigue, espionage, lies and black propaganda.

An elaborate British wartime plot succeeded in convincing Hitler that the Allies were about to stage the bulk of the D-Day landings in Pas de Calais rather than on the Normandy coast - a diversion that proved crucial in guaranteeing the invasion's success.

An intercepted memo - which has only now come to light - picked up by British agents and decoded by experts at Bletchley Park - the decryption centre depicted in the film Enigma - revealed that German intelligence had fallen for the ruse....